"Volatility of Tornadogenesis" and Modes of Storm-scale Variability in VORTEX2 Near- and Far-field Environments

The sensitivity of tornadogenesis to the background synoptic environment, the storm-influenced mesoscale environment, and chaotic intra-storm processes is an active area of research. In this study, 15-member ensembles of supercell simulations were created using the far- and near-field tornadic composite soundings from VORTEX2 (Parker 2014). The far-field sounding was extracted roughly 70 km upstream of the supercell updraft and the near-field sounding was extracted roughly 30 km upstream. This far-field ensemble shows larger variability in terms of tornado production than the near-field ensemble, with some members not producing a tornado, some producing a single tornado, and others producing cycling tornadoes. In all, 93% of storms initialized in the near-field tornadic environment produced a tornado, and 20% of storms initialized in the far-field tornadic environment produced a tornado. The far-field tornadic ensemble of supercells produced less tornadoes than the near-field nontornadic ensemble of supercells from Coffer et al. (2017). Outflow temperatures in the vicinity of the surface vertical vorticity maximum and 1 km AGL updraft speeds are typically warmer and stronger in the near-field ensemble than in the far-field ensemble, but these vary on a case-by-case basis. Empirical orthogonal function analysis reveals that a storm-scale boundary extending to the north of the surface vertical vorticity maximum is a dominant mode of variability in the near-field ensemble. This feature is less evident in the far-field ensemble. These findings show that tornado potential may be influenced by storm-environment interactions and that some storm-scale features may represent the physical manifestation of this relationship.